Root/fs/attr.c

1/*
2 * linux/fs/attr.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 * changes by Thomas Schoebel-Theuer
6 */
7
8#include <linux/module.h>
9#include <linux/time.h>
10#include <linux/mm.h>
11#include <linux/string.h>
12#include <linux/capability.h>
13#include <linux/fsnotify.h>
14#include <linux/fcntl.h>
15#include <linux/security.h>
16
17/**
18 * inode_change_ok - check if attribute changes to an inode are allowed
19 * @inode: inode to check
20 * @attr: attributes to change
21 *
22 * Check if we are allowed to change the attributes contained in @attr
23 * in the given inode. This includes the normal unix access permission
24 * checks, as well as checks for rlimits and others.
25 *
26 * Should be called as the first thing in ->setattr implementations,
27 * possibly after taking additional locks.
28 */
29int inode_change_ok(const struct inode *inode, struct iattr *attr)
30{
31    unsigned int ia_valid = attr->ia_valid;
32
33    /*
34     * First check size constraints. These can't be overriden using
35     * ATTR_FORCE.
36     */
37    if (ia_valid & ATTR_SIZE) {
38        int error = inode_newsize_ok(inode, attr->ia_size);
39        if (error)
40            return error;
41    }
42
43    /* If force is set do it anyway. */
44    if (ia_valid & ATTR_FORCE)
45        return 0;
46
47    /* Make sure a caller can chown. */
48    if ((ia_valid & ATTR_UID) &&
49        (current_fsuid() != inode->i_uid ||
50         attr->ia_uid != inode->i_uid) && !capable(CAP_CHOWN))
51        return -EPERM;
52
53    /* Make sure caller can chgrp. */
54    if ((ia_valid & ATTR_GID) &&
55        (current_fsuid() != inode->i_uid ||
56        (!in_group_p(attr->ia_gid) && attr->ia_gid != inode->i_gid)) &&
57        !capable(CAP_CHOWN))
58        return -EPERM;
59
60    /* Make sure a caller can chmod. */
61    if (ia_valid & ATTR_MODE) {
62        if (!inode_owner_or_capable(inode))
63            return -EPERM;
64        /* Also check the setgid bit! */
65        if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
66                inode->i_gid) && !capable(CAP_FSETID))
67            attr->ia_mode &= ~S_ISGID;
68    }
69
70    /* Check for setting the inode time. */
71    if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
72        if (!inode_owner_or_capable(inode))
73            return -EPERM;
74    }
75
76    return 0;
77}
78EXPORT_SYMBOL(inode_change_ok);
79
80/**
81 * inode_newsize_ok - may this inode be truncated to a given size
82 * @inode: the inode to be truncated
83 * @offset: the new size to assign to the inode
84 * @Returns: 0 on success, -ve errno on failure
85 *
86 * inode_newsize_ok must be called with i_mutex held.
87 *
88 * inode_newsize_ok will check filesystem limits and ulimits to check that the
89 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
90 * when necessary. Caller must not proceed with inode size change if failure is
91 * returned. @inode must be a file (not directory), with appropriate
92 * permissions to allow truncate (inode_newsize_ok does NOT check these
93 * conditions).
94 */
95int inode_newsize_ok(const struct inode *inode, loff_t offset)
96{
97    if (inode->i_size < offset) {
98        unsigned long limit;
99
100        limit = rlimit(RLIMIT_FSIZE);
101        if (limit != RLIM_INFINITY && offset > limit)
102            goto out_sig;
103        if (offset > inode->i_sb->s_maxbytes)
104            goto out_big;
105    } else {
106        /*
107         * truncation of in-use swapfiles is disallowed - it would
108         * cause subsequent swapout to scribble on the now-freed
109         * blocks.
110         */
111        if (IS_SWAPFILE(inode))
112            return -ETXTBSY;
113    }
114
115    return 0;
116out_sig:
117    send_sig(SIGXFSZ, current, 0);
118out_big:
119    return -EFBIG;
120}
121EXPORT_SYMBOL(inode_newsize_ok);
122
123/**
124 * setattr_copy - copy simple metadata updates into the generic inode
125 * @inode: the inode to be updated
126 * @attr: the new attributes
127 *
128 * setattr_copy must be called with i_mutex held.
129 *
130 * setattr_copy updates the inode's metadata with that specified
131 * in attr. Noticeably missing is inode size update, which is more complex
132 * as it requires pagecache updates.
133 *
134 * The inode is not marked as dirty after this operation. The rationale is
135 * that for "simple" filesystems, the struct inode is the inode storage.
136 * The caller is free to mark the inode dirty afterwards if needed.
137 */
138void setattr_copy(struct inode *inode, const struct iattr *attr)
139{
140    unsigned int ia_valid = attr->ia_valid;
141
142    if (ia_valid & ATTR_UID)
143        inode->i_uid = attr->ia_uid;
144    if (ia_valid & ATTR_GID)
145        inode->i_gid = attr->ia_gid;
146    if (ia_valid & ATTR_ATIME)
147        inode->i_atime = timespec_trunc(attr->ia_atime,
148                        inode->i_sb->s_time_gran);
149    if (ia_valid & ATTR_MTIME)
150        inode->i_mtime = timespec_trunc(attr->ia_mtime,
151                        inode->i_sb->s_time_gran);
152    if (ia_valid & ATTR_CTIME)
153        inode->i_ctime = timespec_trunc(attr->ia_ctime,
154                        inode->i_sb->s_time_gran);
155    if (ia_valid & ATTR_MODE) {
156        umode_t mode = attr->ia_mode;
157
158        if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
159            mode &= ~S_ISGID;
160        inode->i_mode = mode;
161    }
162}
163EXPORT_SYMBOL(setattr_copy);
164
165int notify_change(struct dentry * dentry, struct iattr * attr)
166{
167    struct inode *inode = dentry->d_inode;
168    mode_t mode = inode->i_mode;
169    int error;
170    struct timespec now;
171    unsigned int ia_valid = attr->ia_valid;
172
173    if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
174        if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
175            return -EPERM;
176    }
177
178    if ((ia_valid & ATTR_MODE)) {
179        mode_t amode = attr->ia_mode;
180        /* Flag setting protected by i_mutex */
181        if (is_sxid(amode))
182            inode->i_flags &= ~S_NOSEC;
183    }
184
185    now = current_fs_time(inode->i_sb);
186
187    attr->ia_ctime = now;
188    if (!(ia_valid & ATTR_ATIME_SET))
189        attr->ia_atime = now;
190    if (!(ia_valid & ATTR_MTIME_SET))
191        attr->ia_mtime = now;
192    if (ia_valid & ATTR_KILL_PRIV) {
193        attr->ia_valid &= ~ATTR_KILL_PRIV;
194        ia_valid &= ~ATTR_KILL_PRIV;
195        error = security_inode_need_killpriv(dentry);
196        if (error > 0)
197            error = security_inode_killpriv(dentry);
198        if (error)
199            return error;
200    }
201
202    /*
203     * We now pass ATTR_KILL_S*ID to the lower level setattr function so
204     * that the function has the ability to reinterpret a mode change
205     * that's due to these bits. This adds an implicit restriction that
206     * no function will ever call notify_change with both ATTR_MODE and
207     * ATTR_KILL_S*ID set.
208     */
209    if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
210        (ia_valid & ATTR_MODE))
211        BUG();
212
213    if (ia_valid & ATTR_KILL_SUID) {
214        if (mode & S_ISUID) {
215            ia_valid = attr->ia_valid |= ATTR_MODE;
216            attr->ia_mode = (inode->i_mode & ~S_ISUID);
217        }
218    }
219    if (ia_valid & ATTR_KILL_SGID) {
220        if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
221            if (!(ia_valid & ATTR_MODE)) {
222                ia_valid = attr->ia_valid |= ATTR_MODE;
223                attr->ia_mode = inode->i_mode;
224            }
225            attr->ia_mode &= ~S_ISGID;
226        }
227    }
228    if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
229        return 0;
230
231    error = security_inode_setattr(dentry, attr);
232    if (error)
233        return error;
234
235    if (ia_valid & ATTR_SIZE)
236        down_write(&dentry->d_inode->i_alloc_sem);
237
238    if (inode->i_op->setattr)
239        error = inode->i_op->setattr(dentry, attr);
240    else
241        error = simple_setattr(dentry, attr);
242
243    if (ia_valid & ATTR_SIZE)
244        up_write(&dentry->d_inode->i_alloc_sem);
245
246    if (!error)
247        fsnotify_change(dentry, ia_valid);
248
249    return error;
250}
251
252EXPORT_SYMBOL(notify_change);
253

Archive Download this file



interactive